Passivated polycrystalline semiconductors quantum well/superlattice structures fabricated thereof

Abstract

The internal grain boundaries and intergranular spaces of polycrystalline semiconductor material may be passivated with an amorphous material, to substantially eliminate the dangling bonds at the internal grain boundaries. The passivated polycrystalline material of the present invention exhibits a lower electrically active defect density at the grain boundaries and intergranular space compared to unpassivated polycrystalline material. Moreover, large classes of amorphous passivating materials may be used for each known semiconductor material so that the passivating process may be readily adapted to existing process parameters and other device constraints. Passivated polycrystalline material may be employed to form the well or low energy bandgap layer of a quantum well device or superlattice, while still maintaining the required tunneling effect. By freeing quantum well devices from the requirement to use monocrystalline well material deeper wells may be produced, and a wider range of materials may be used, with high yields and low cost processes.

That which we claim is: 
     
       1. A quantum well structure for a semiconductor device comprising: first and second barrier layers; and   a passivated polycrystalline semiconductor well layer formed between said first and said second barrier layers, said passivated polycrystalline semiconductor well layer and said first and second barrier layers having a band-edge offset therebetween; said passivated polycrystalline semiconductor well layer comprising a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat, and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds, wherein said plurality of crystalline grains comprise silicon grains and wherein said amorphous passivating agent comprises at least one of amorphous-silicon dioxide, amorphous-phosphorous, amorphous-phosphorous oxide, and amorphous-silicon germanium oxide.   
     
     
       2. A quantum well structure for a semiconductor device comprising: first and second barrier layers; and   a passivated polycrystalline semiconductor well layer formed between said first and said second barrier layers, said passivated polycrystalline semiconductor well layer and said first and second barrier layers having a band-edge offset therebetween; said passivated polycrystalline semiconductor well layer comprising a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat, and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds, wherein said plurality of crystalline grains comprise germanium and wherein said amorphous passivating agent comprises at least one of amorphous-germanium oxide, amorphous-phosphorous,, amorphous-phosphorous oxide, and amorphous-germanium silicon oxide.   
     
     
       3. A quantum well structure for a semiconductor device comprising: first and second barrier layers; and   a passivated polycrystalline semiconductor well layer formed between said first and said second barrier layers, said passivated polycrystalline semiconductor well layer and said first and second barrier layers having a band-edge offset therebetween; said passivated polycrystalline semiconductor well layer comprising a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat, and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds, wherein said plurality of crystalline grains comprise a III-V compound and wherein said amorphous passivating agent comprises at least one of amorphous-selenium, amorphous-tellurium, amorphous-sulphur, amorphous-germanium, amorphous-arsenic selenium, amorphous-indium selenium, amorphous-gallium oxide, amorphous-germanium selenium, and amorphous-gallium selenium.   
     
     
       4. The quantum well structure of claims 1, 2 or 3 wherein a superlattice is formed by combining at least two of said quantum well structures. 
     
     
       5. The quantum well structure of claims 1, 2 or 3 wherein said passivated polycrystalline semiconductor well layer has an energy bandgap which is lower than energy bandgaps of said first and second barrier layers. 
     
     
       6. The quantum well structure of claims 1, 2 or 3 wherein said first barrier layer is formed on a semiconductor substrate. 
     
     
       7. The quantum well structure of claim 6 wherein said semiconductor substrate comprises a silicon substrate having an insulating amorphous silicon dioxide layer thereon. 
     
     
       8. The quantum well structure of claim 7 wherein said first and second barrier layers comprise gallium aluminum arsenide. 
     
     
       9. The quantum well structure of claim 8 wherein said first and second barrier layers comprise passivated polycrystalline gallium aluminum arsenide. 
     
     
       10. A passivated polycrystalline semiconductor material comprising: a polycrystalline semiconductor material including a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat; and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds; wherein said polycrystalline semiconductor material comprises silicon, and wherein said amorphous passivating agent comprises at least one of amorphous-silicon dioxide, amorphous-phosphorous, amorphous-phosphorus oxide, and amorphous-silicon germanium oxide.   
     
     
       11. A passivated polycrystalline semiconductor material comprising: a polycrystalline semiconductor material including a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat; and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds; wherein said passivated polycrystalline semiconductor material comprises germanium, and wherein said amorphous passivating agent comprises at least one of amorphous-germanium oxide, amorphous-phosphorous, amorphous-phosphorous oxide, and amorphous-germanium silicon oxide.   
     
     
       12. A passivated polycrystalline semiconductor material comprising: a polycrystalline semiconductor material including a plurality of crystalline grains having internal grain boundaries therebetween, said internal grain boundaries having dangling bonds thereat; and an amorphous passivating agent in said grain boundaries for bonding to said dangling bonds; wherein said passivated polycrystalline semiconductor material comprises a group III-V compound, and wherein said amorphous passivating agent comprises at least one of amorphous-selenium, amorphous-tellurium, amorphous-sulphur, amorphous-germanium, amorphous-arsenic selenium, amorphous-indium selenium, amorphous-gallium oxide, amorphous-germanium selenium, and amorphous-gallium selenium.   
     
     
       13. The passivated polycrystalline semiconductor material of claim 12 in combination with a silicon substrate having an insulating amorphous silicon dioxide layer thereon.